In general, a backlight unit used for a display device, such as a liquid crystal display (LCD), is a component disposed at the rear of a display panel having no light emitting function of its own so as to uniformly project planar light. The backlight unit may be classified as a direct type backlight unit or an edge type backlight unit, according to the position of a light source for emitting actual light. In the direct type backlight unit, light sources are disposed below a display panel and emit light therethrough, so that it is advantageous for a large-sized display. In the edge type backlight unit, a light source is disposed at the edge of a display panel so that it is advantageous for a thin, compact display.
FIG. 1 is a sectional view illustrating a configuration of a related art direct type backlight unit.
As shown in FIG. 1, the related art direct type backlight unit includes a plurality of light sources 120, a reflective plate 110, a light guide plate 130, a plurality of diffusion films 140 and 150, a condensing film 160, and a protective film 170.
Moreover, in the case of the related art direct type backlight unit, since the brightness at the right upper portions of the light sources and the brightness between the light sources are different, Mura defects may occur. As shown in FIG. 1, the plurality of diffusion films 140 and 150 are used to allow the light emitted from the light sources to diffuse across an entire plane, in order to prevent the Mura defects. However, due to the plurality of diffusion films, the manufacturing costs of the related art direct type backlight unit are high and its thickness is greater.
Moreover, in relation to the related art direct type backlight unit, since a plurality of optical films are stacked with a layer of air therebetween, light may be refracted at the interface between the optical film and the air layer. As a result, light transmittance may be deteriorated.